Prosthetic implant with biplanar angulation and compound angles

ABSTRACT

A prosthetic implant, and more particularly, with a prosthetic implant having biplanar angulation and that can be inserted into a disk area generally straight using a posterolateral approach.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/336,753, filed Dec. 17, 2008, which is incorporated herein byreference and made a part hereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a prosthetic implant, and more particularly,with a prosthetic implant having a biplanar angulation to permitinsertion straight along a diagonal angle into a disk space.

2. Description of the Related Art

Spinal fusion is a commonly performed procedure. In a typical spinalfusion operation, a surgeon places a mechanical container, commonlyknown as a cage, between at least two adjacent vertebrae of the spine.This container contains or is later filled with bone graft whicheventually incorporates into the adjacent vertebrae and creates a solidfusion. Interbody cages are placed in the disk space following removalof the disk. The cage can be surgically placed via several approaches,such as anteriorly through the abdomen, posteriorly through the spinalcanal, posterolaterally through the neuroforamen of the vertebra, andtransversely from a side of the spine. A goal of the surgical approachis to minimize trauma to adjacent structures and incision size.

A challenge to the placement of cages is the attainment of properfitment between the adjacent vertebrae. It is important that a cagesurface fits flushly against the endplates of the adjacent vertebrae. Ifa cage fits poorly, the cage could loosen, causing poor fixation andpotential re-operation. The disk space, where the cage is placed, is notparallel. The space is angulated such that it is wider anteriorly thanposteriorly. This angulation is termed lordosis.

Several cage designs have been proposed in the prior art. Brantigan(U.S. Pat. No. 4,834,757) describes a square shaped cage which isimpacted in between vertebrae. Michelson (U.S. Pat. No. 5,015,247)describes a straight threaded cage which is screwed into the disk space.Brantigan (U.S. Pat. No. 5,425,772) and Michelson (U.S. Pat. No.6,302,914) describe a cage with a built in single-plane lordotic angleto improve fitment between adjacent vertebrae. These cages are designedfor posterior or anterior placement.

The placement of cages from posterior, lateral, and anterior approachesraise concerns about potential impingement upon important anatomicalstructures. Such structures are the spinal canal, the spinal nerves, andthe abdominal vasculature, respectively. The posterolateral approach,also called the transforamenal approach, is gaining popularity as thepreferred approach for the placement of intervertebral fusion cages.Typically, cages designed for this approach are “banana shaped,” asexemplified by Varga, et al (U.S. Pat. No. 6,579,318).

A significant difficulty with banana-type cages is that their placementrequires cage rotation at the time of placement to seat the cage inplace. The cage is inserted at a 45 degree lateral angle into the diskspace (the maximum angle limited by anatomical structures) and is thenrotated a further 45 degrees within the disk space for proper placement.This rotational step is difficult in that it occurs blindly inside thedisk space. Incomplete rotation frequently occurs, resulting in poorcage fitment, with potential loosening and reoperation.

If a Brantigan (U.S. Pat. No. 4,834,757) cage were inserted in adiagonal or non-straight trajectory, it would not have flush contactwith the adjacent vertebrae due to the lordotic angle of the disk space.Furthermore, a standard lordotic cage, such as Michelson (U.S. Pat. No.6,302,914), would have its lordotic angle in the incorrect orientationfor proper fitment if placed diagonally.

What is needed is a cage that can be placed via the posterolateralapproach in a straight manner and that does not require a furtherrotation for placement. Desirably, such a cage will be placed at astraight angle relative to an anterior-posterior axis and, preferably,at a diagonal or angle, such as approximately 45 degrees and reside in adiagonal configuration within the disk space.

SUMMARY OF THE INVENTION

Accordingly, one object of the invention is to provide a cage having abiplanar angulation.

Another object of the invention is to provide a cage that has a biplanarangulation and that may be inserted straight into a disk space, at anangle or diagonally relative to the anterior-posterior axis of thespine.

Still another object of the invention is to provide a cage having abiplanar angulation and that minimizes or eliminates the need forrotation after the cage is inserted into the disk space.

Yet another object of the invention is to provide a cage having lateralslots or channels for insertion of a tool or instrument to facilitateplacement of the cage.

In one aspect, this invention comprises a fusion cage comprising a cagebody having a plurality of surfaces, the plurality of surfacescooperating to define a multi-planar angulation adapted to achievesubstantially flush fitment in a disk space between adjacent vertebraewhen the fusion cage is inserted in the disk space.

In another aspect, this invention comprises a method for fusing bones,the method comprising the steps of providing a cage adapted to beinserted into a disk area substantially diagonally or in an angleddirection with respect to an anterior-posterior axis, the cage having afirst surface lying in a first plane and a second surface lying in asecond plane, and inserting the cage in the substantially diagonal orangled direction such that the first and second surfaces engage asurface of a first vertebrae and a second vertebrae substantially flush.

These and other objects and advantages of the invention will be apparentfrom the following description, the accompanying drawings and theappended claims.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is a perspective view of a cage in accordance with one embodimentof the invention showing the cage placed in a disk space;

FIG. 2 is a view, taken along the line 2-2 in FIG. 1, showing the cageinserted straight and at a diagonal or an angle with respect to ananterior-posterior axis;

FIG. 3 is a perspective view showing various details of the cage shownin FIGS. 1 and 2;

FIG. 4 is another perspective view of the cage of FIG. 1;

FIG. 5 is a perspective view of the cage with various projection linesshowing the dimensional relationships between the various line segmentsto illustrate the biplanar angulation or compound angles formed by thevarious surfaces of the cage;

FIG. 5A is view showing imaginary planes corresponding to the superiorand inferior surfaces of the cage, showing their relative relationshipand multi-planar or bi-planer angulation;

FIG. 5B is a view, taken in the direction of arrow A in FIG. 5A, showingthe relationship of the planes and biplanar angulation of the surfaces;

FIG. 6 is a front view of the cage;

FIG. 7 is a rear view of the cage;

FIG. 8 is a side view of the cage shown in FIG. 1, showing the variousrelationships and dimensions and relative dimensions of the variouscorners of the cage;

FIGS. 9 and 10 are illustrative embodiments showing differentmulti-planar or biplanar angulations;

FIG. 11 is a cross-sectional view taken along the line 11-11 in FIG. 5;

FIG. 12 is a diagonal view taken along the line 12-12 in FIG. 5;

FIG. 13 is a sectional view taken along the line 13-13 in FIG. 5;

FIG. 14 is a fragmentary exploded perspective view of a portion of acage and an insertion tool;

FIG. 15 is a perspective view of yet another embodiment of the cage ofFIG. 1;

FIG. 16 is a front view of the cage;

FIG. 17 is a rear view of the cage;

FIG. 18 is a perspective view of the cage similar to FIG. 5;

FIGS. 19A and 19B are views similar to FIGS. 5A and 5B, respectively;

FIG. 20A illustrates a cage placed in a space between two disks;

FIG. 20B is a view taken along line 20B-20B of FIG. 20A;

FIG. 20C is a view taken along line 20C-20C of FIG. 20A;

FIG. 20D is a view taken along line 20D-20D of FIG. 20A;

FIG. 21A is a view similar to FIG. 20A showing use of another cage;

FIG. 21B is a view taken along line 21B-21B of FIG. 21A;

FIG. 21C is a view taken along line 21C-21C of FIG. 21A;

FIG. 21D is a view taken along line 21D-21D of FIG. 21A;

FIG. 22A is a view similar to FIGS. 20A and 21A;

FIG. 22B is a view taken along line 22B-22B of FIG. 21A;

FIG. 22C is a view taken along line 22C-22C of FIG. 21A;

FIG. 22D is a view taken along line 22D-22D of FIG. 21A; and

FIG. 23 is a is a perspective view of another embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1-10, a prosthetic implant or fusion cage 10 isshown for insertion and use in a disk space or disk area 11 between afirst vertebra 12 and second vertebra 14. In the illustration beingdescribed, the first vertebra 12 has a first or superior surface 12 aand the second vertebra 14 has a second or inferior surface 14 a, asbest illustrated in FIG. 1. The cage 10 is inserted straightposterolaterally, also called a transforamenal approach, into the diskarea 11 between the first vertebra 12 and second vertebra 14. Asdescribed and shown, the cage 10 is inserted on a diagonal or angleddirection with respect to an anterior-posterior axis AP (FIG. 2), suchas in the direction of arrow 16 as shown.

Notice in FIGS. 3 and 4 that the cage 10 comprises a superior or topsurface 18 and a generally opposing inferior or bottom surface 20. Inthe illustration being described, note that the surfaces 18 and 20 areserrated or comprise teeth 22 to facilitate preventing the cage 10 fromloosening or becoming displaced after the cage 10 is placed in the diskarea 11 between the first vertebra 12 and the second vertebra 14. Thecage 10 is adapted or configured to comprise the surfaces 18 and 20 thatcooperate to define a biplanar angulation and that cooperate to definemultiple angles or at least one compound angle as described herein. Therelative angulation between surfaces 18 and 20 facilitate full or flushsurface contact between the vertebrae surfaces 12 a and 14 a and thesurfaces 18 and 20, respectively, of the cage 10.

As illustrated in FIGS. 3 and 4, the surfaces 18 and 20 comprise aninterior wall 18 a and 20 a, respectively, that define generally ovalapertures or openings 24 and 26, for receiving bone graft material. Notethat the cage 10 further comprises a front portion, surface or end 28and a rear surface or end 30 as shown. The front portion, surface or end28 comprises a plurality of angled surfaces 28 c and 28 d, as shown,that cooperate to define a nose, prow or angled frontal portion for easeof substantially straight or linear insertion and placement into thedisk area 11 using a posterolateral or transforamenal approach.

The rear surface or end 30 comprises an interior wall 30 a having athreaded aperture 40 for receiving an instrument or bone graft materialafter the cage 10 is inserted substantially straight or linearly intothe disk area 11 using the posterolateral or transforamenal approach.

The cage 10 further comprises a side or third surface 42 and a generallyopposing side or fourth surface 44 as shown. Note that the third surface42 comprises a plurality of interior walls 42 a and 42 b that defineapertures 46 and 48, respectively. Similarly, fourth surface 44comprises interior walls 44 a and 44 b that define apertures 50 and 52,respectively, as shown. As illustrated, the apertures 46 and 48 aregenerally opposed to the apertures 50 and 52, respectively, and providelateral openings adapted to permit graft material to be inserted into anopen cage area 54 for fusing the vertebrae 12 and 14 together. Thus, itshould be understood that the bilateral openings or apertures 46, 48, 50and 52 facilitate insertion of bone graft material (not shown) and forbone ingrowth. The inferior and superior openings 24 and 26 furtherfacilitate bone ingrowth.

The surfaces 42 and 44 each comprise a plurality of generally U-shapedwalls or surfaces 42 c, 42 d and 44 c, 44 d, respectively, to define afirst lateral slot 60 and a second lateral slot 62, respectively, forfacilitating the placement of the cage 10 using an insertion tool or asurgical instrument 61 (FIG. 14). Notice that the lateral slots 60 and62 are asymmetrical to allow for directional coupling to an insertiontool or surgical instrument 61. In this regard, notice that the slot 60has a dimension D1 that is greater than a dimension D2 of the slot 62.The lateral slots 60 and 62 are adapted to receive a generallycomplementary shaped inter-fitting members or projections 63 and 65,respectively, of the insertion tool or surgical instrument 61.

The insertion tool or surgical instrument 61 has a hollow tubularportion 61 a that receives a rotatable shaft extension 67 having an end69 that is threaded so that it can be screwed or threaded into thethreaded aperture 40, as illustrated. During use, the surgeon wouldplace the rotatable shaft extension 67 until the cage 10 becomes securedor fixed to the insertion tool or surgical instrument 61.

After placement of the cage 10, the rotatable shaft extension 67 isrotated counterclockwise from the cage 10. Note that the insertion toolor surgical instrument 61 or tubular portion 61 a may have indicia 71for indicating to the surgeon or user the proper orientation of the cage10, thereby reducing or eliminating the chance that the cage 10 would beimproperly placed, for example, upside down into the disk area 11.

Referring now to FIGS. 3-10, the relative relationship of the surfaces18 and 20, multiplanar or biplanar angulation and compound angle(s) theydefine will now be described. For ease of illustration, FIGS. 5-10 showvarious line projections or line segments corresponding to lines orsegments between various boundary corners or points or edges of the cage10. The points are identified and labeled with the letters A-F. Thevarious relationships between and/or among the line segments and othersegments will be used for ease of understanding to illustrate ordemonstrate the biplanar angulation or compound angles of the cage 10 inthis illustration. The “>” designation is understood to mean that adimension of a segment is larger than the dimension of the segment(s) towhich it is compared, “<” means the dimension is less, and “=” means thedimension of the segments is equal. For example, “CD>AB” means that theportion of the cage 10 associated with line segment CD comprises adimension that is greater than the portion of the cage 10 associatedwith segment AB.

Returning to the description in the illustration of FIGS. 5-8, note thatthe line segment length C-D>A-B>E-F>G-H, and the area defined by ACDB inFIG. 5 is greater than the area GEFH. As illustrated in FIGS. 5-8, thedimension between the line segments A-C and B-D gets smaller when movingfrom line C-D to A-B. Likewise, the cage 10 has a compound or biplanarangulation so that a cross-sectional height dimension (as viewed in FIG.5) of the cage 10 gets smaller from segment C-D as it moves to everyother segment A-B, G-H and E-F.

FIG. 5A illustrates imaginary planes P1 and P2 in which the surfaces 18and 20, respectively, lie. FIG. 5B shows a view taken in the directionof arrow A in FIG. 5A and generally perpendicular to the plane P2showing the biplanar angulation or relative tilt (when viewed from leftto right in the FIG. 5B and toward G-H). In the example, the surfaces 18and 20 converge along both a longitudinal axis from a first point, suchas the end 28, to a second point such as the rear surface or end 30. Theplanes P1 and P2 and surfaces 18 and 20 also converge in a directionfrom segment C-D to G-H in the illustration and also when viewed in adirection generally perpendicular to that longitudinal axis as shown inFIGS. 5-A, 5B and 5C. Thus, the cage 10 and surfaces 18 and 20 definenumerous angles, such as angles BA1, BA2, BA3 and BA4 shown in FIG. 4.The angles are all different in the illustration.

Stated another way, the cage 10 comprises a longitudinal axis LA (FIG.3) and a cross-sectional axis CSA (FIG. 3) that is generallyperpendicular to the longitudinal axis LA. In the illustration beingdescribed in FIGS. 1-14, the cage 10 is symmetrical about a longitudinalhorizontal plane LHP (FIG. 4) along the longitudinal center axis (FIG.3), but is non-symmetrical in a longitudinal vertical plane LVP (FIG.3). In one illustration, the cage 10 assumes a trapezoid (FIG. 11) in avertical cross-sectional plane that is generally perpendicular to thelongitudinal center axis, such as the imaginary plane along line 11-11in FIG. 5. It should be understood, however, that the cage 10 couldassume another shape, such as a trapezium (see FIGS. 15-19B), ellipsoid,circular, oval, arcuate or other shape. Other illustrative embodimentsare shown in FIGS. 15-23 described later herein.

One important feature of the cage 10 is that the opposing surfaces 18and 20 in the illustration provide, are arranged or are adapted tocooperate to define one or more compound angles or a biplanar angulationso that the surfaces 18 and 20 become in substantially flush contactwith the surfaces 12 a and 14 a, respectively, when the cage 10 isinserted substantially straight or linearly on a diagonal or angle intothe disk area 11 using a posterolateral or transforamenal approach and,if necessary, rotated as described herein.

FIG. 8 is an illustration corresponding to the embodiments of FIGS. 3-7illustrating CD being greater than AB which is greater than EF which inturn is greater than GH. It should be understood, however, that thedegree of the biplanar angulation or compound angle will be selected orchanged and will depend upon the relative relationship or orientationbetween the disk surfaces 12 a and 14 a. Several other illustrativeembodiments are shown in FIGS. 9-10. For example, FIG. 9 illustrates anembodiment wherein the cage 10 has dimensions such that the line segmentCD>AB=EF>GH. FIG. 10 illustrates an embodiment where line segmentCD>AB<EF>GH. As described later herein, the user will select the cage 10having the desired biplanar angulation in response to the disk area 11and the relative relationship of the vertebrae surfaces 12 a and 14 a.This selection and placement will now be described.

During a surgical procedure it should be understood that the cage 10 isinserted generally straight or linearly at an angle or on a diagonaltrajectory relative to the anterior-posterior axis AP (FIG. 2) using aposterolateral or transforamenal approach. As mentioned, the cage 10 andthe biplanar angulation or compound angle(s) defined by surfaces 18 and20 will be selected and adapted depending upon the relative relationshipbetween the surfaces 12 a and 14 a. In general, the angle Θ (FIG. 2) ofinsertion increases, the length differences between the segments EF-CDwill be decreased and the length differences between the segments AB-GHwill also be decreased or lesser. In one embodiment, the cage is beingrotated from an angle parallel to the intervertebral lordotic angle toan angle perpendicular to the intervertebral lordotic angle. SegmentsEF-CD and AB-GH no longer have to conform to this lordotic angle in thistrajectory and therefore their length differences are decreased.

As a size of the cage 10 increases, a length difference, for example,between segments EF-CD will be greater as the cage 10 gets largerbecause a larger amount of the lordotic angle is covered by the cage,and segments or dimensions AB-GH will also be greater. FIGS. 20A-20D,21A-21D and 22A-22D further illustrate these concepts. All else beingequal, larger cages 10 require larger segment differences. A tiny cage10 covers very little length of the lordosis, so the difference in sidelength will be small.

In the illustration in FIGS. 20A-20D, a selected cage 10 is insertedusing a posterolateral or transforamenal approach and rotated such thatits longitudinal axis is generally parallel to the anterior-posterioraxis AP as shown. In this illustration, the cage 10 may have arelatively large longitudinal angulation (the angulation BA3 associatedwith side 42) as illustrated in FIG. 20B. Note, however, that thesurfaces 12 a and 14 a in the illustration are angled not onlyposterolaterally, but also slightly in a lateral direction (i.e., alonga cross-sectional angulation that is generally perpendicular to thelongitudinal axis of the cage 10), as illustrated in FIG. 20B. Given theslight angulation, the cage 10 may have only a slight cross-sectionalangulation (that is, the angles BA1 and BA2, illustrated in FIGS. 20Cand 20D, respectively).

FIGS. 21A-21D illustrate a similar relationship between surfaces 12 aand 14 a. However, note that the cage 10 is inserted and rotated orpivoted such that it is angled with respect to the anterior-posteriorcenter line. In view of this positioning, note that the user may selecta cage 10 wherein the surfaces 12 a and 14 a define the angle BA3 thatis less than the angle BA3 associated with the embodiment illustrated inFIG. 20B. Note that the cross-sectional dimension (i.e., those anglesBA1 and BA2 illustrated in FIGS. 21C and 21D) will be slightly largerthan those corresponding angles illustrated in FIGS. 20C and 20D, asshown.

FIGS. 22A-22D show another extreme placement of the cage 10, wherein thecage 10 is situated such that its longitudinal axis is generallyperpendicular to the anterior-posterior axis. In this position, notethat the longitudinal angle is associated with the side 42 (that is, theangle BA3 in the illustration), but generally corresponds to the angle(labeled DA in FIG. 22B) defined by the disk surfaces 12 a and 14 a.Compare this cage 10 to the cage 10 in the illustration describedearlier herein relative to the embodiment of FIG. 20B. Note the cage 10is selected and adapted to conform to the relationship of the surfaces12 a and 14 a as well as the position in which the cage 10 is going tobe inserted into the disk area 11 between the surfaces 12 a and 14 a.

Continuing with the illustration, a cage 10 is shown in FIGS. 22A-22D,having a longitudinal angulation that is slight, as illustrated in FIG.22B, given the lateral placement of the cage 10 in the disk area 11.However note that the cross-sectional angulation and angles BA1 (FIG.22C) and BA2 (FIG. 22D) may be relatively greater when compared to thesame angles illustrated in FIGS. 20C and 20D.

Advantageously, the implant, system and method provides means foradapting and selecting a cage 10 in response to the relationship betweenthe surfaces 12 a and 14 a as well as the placement of the cage 10 usinga posterolateral approach and the position of the cage 10 in the diskarea 11. In some cases, it may be necessary to use a cage 10 havinglarger or smaller longitudinal angles BA3 and BA4 and smallercross-sectional angles BA1 and BA2, while in other environments it maybe desired to use a cage 10 having relatively larger cross-sectionalangles BA1 and BA2 and smaller biplanar angles BA3 and BA4. The anglesBA1 and BA2 can be changed relative to each other as can angles BA3 andBA4.

Thus, it should be appreciated that the invention provides a cage 10having biplanar and angulation defining compound angles that can adaptto various environments such that the surfaces 18 and 20 provide a snugfit against the surfaces 12 a and 14 a, respectively.

As alluded to earlier herein, the cage 10 could assume different shapes,such as trapezium, ellipsoid, circular, oval, arcuate or other shapes.In this regard, and as described earlier herein, the embodiment of FIGS.1-14 illustrate a cage 10 that is generally symmetrical about thelongitudinal horizontal plane (FIG. 4). FIGS. 15-19B illustrate anotherembodiment, similar to the embodiment in FIGS. 1-14 wherein the cage 10is not symmetrical about the longitudinal horizontal plane asillustrated in FIGS. 15-17. The parts in this embodiment are the same orsimilar to the parts in the embodiments of FIGS. 1-14 and those same orsimilar parts have been identified with the same part numbers, exceptthat a prime mark (“ ”) has been added to the part numbers of theembodiment shown in FIGS. 15-19B.

In this illustrative embodiment, the cage 10 is not symmetrical aboutthe longitudinal horizontal plane LHP illustrated in FIGS. 16 and 17,and the surfaces 18, 20, 42 and 44 cooperate to define a trapezium incross-section as shown.

As illustrated in FIG. 18 and as with the embodiment being describedearlier herein, various relationships between the segments may bedefined. For example, as illustrated in FIGS. 15-18, the line segment KLis greater than IJ is greater than MN is greater than OP and the areadefined by IKLJ in FIG. 18 is greater than the area OMNP. As with theprior embodiment, these various dimensions and relationships may bechanged, modified or adapted to the particular environment or disk area11 in which the cage 10 is going to be used.

FIGS. 19A-19B are similar to the imaginary planes shown in FIGS. 5A and5B. These planes, however, show the non-symmetry of the surfaces 18 and20 about the longitudinal horizontal plane. By comparison, note theplanes P1 and P2 illustrated FIG. 5B show the planes P1 and P2 beinggenerally symmetrical about the longitudinal horizontal plane. As withthe prior embodiment, the cage 10 in FIG. 15 is also asymmetrical aboutthe longitudinal plane.

FIG. 23 illustrates yet another embodiment of the invention illustratinga different shape of the cage 10 having biplanar angulation. In thisembodiment, the surfaces 18 and 20 are bowed, convex or arcuately shapedas shown. Similar parts are identified with a double prime mark.

Thus, it should be understood that the cage 10 is selected and/oradapted to comprise a biplanar angulation and to permit aposterior-lateral insertion into the disk area 11. The cage 10 isselected or adapted such that it will provide a flush fitmet in alordotic disk space when placed diagonally via a posterolateralapproach. Advantageously, the cage 10 provides biplanar angulation toallow for full surface contact with the surfaces 12 a and 14 a of theadjacent vertebrae 12 and 14, respectively, when placed at the angled ordiagonal trajectory. Note that the cage 10 is inserted in the angled ordiagonal trajectory and that the superior and inferior cage surfaces 18and 20 are in flush or substantially flush engagement with the surfaces12 a and 14 a.

It should be understood that while the embodiments illustrated in FIGS.1-10 show a polygonal or multi-sided shaped cage 10, the cage 10 couldtake other configurations, such as elliptical, circular or the like. Theimportant feature is that the cage 10 is adapted to provide a biplanarangulation of surfaces 18 and 20 that cooperate to define a compoundangle or a biplanar angulation that facilitate a generally orsubstantially flush fit against surfaces 12 a and 14 a, respectively, ofthe vertebrae during generally straight insertion using a posteriorlateral approach.

During use, the insertion tool or surgical instrument 61 (FIG. 14) isscrewed to the cage 10 as illustrated in FIGS. 1 and 2, the cage 10 isplaced using a posterolateral or transforamenal approach and insertedinto the disk area 11 (FIG. 1) in a generally straight or linear manner.In the illustration being described, the cage 10 provides means andapparatus that can be placed via a posterolateral approach in arelatively straight manner which reduces or eliminates the need torotate the cage 10, which can reduce or minimize incorrect orientationor impingement upon important anatomical structures, such as the spinalcanal, spinal nerves, abdominal vasculature. The surgeon may use theinsertion tool or surgical instrument 61 (FIG. 14) inserted into thelateral slots 60 and 62 to facilitate placement and proper positioning.Note that the nose or front portion 28 of the cage 10 is adapted tofacilitate insertion into the disk area 11. The cage 10 may be pivotedor rotated to a proper position as suggested in FIGS. 20A-22D. Graftmaterial may be inserted in a conventional manner into the cage 10.Typically, the graft is placed prior to the insertion of the cage. Thecage 10 is then placed using a posterolateral or transforamenal approachand rotated or pivoted if necessary. Thereafter, the patient is closedand the procedure is finished in a conventional manner.

Advantageously, the prosthetic implant or fusion cage 10 provides manyadvantages, some of which include:

-   -   a fusion cage wherein the plurality of surfaces cooperate to        define a biplanar angulation;    -   a fusion cage wherein the cage body has a first surface        generally opposed to a second surface, the first and second        surfaces cooperating to define a compound angle and defining a        biplanar angulation;    -   a fusion cage wherein the at least one of the first or second        surfaces are arcuate or convex in cross-section;    -   a fusion cage wherein the first surface and the second surface        converge along a longitudinal axis and in a direction generally        perpendicular to the longitudinal axis, the first and second        surfaces cooperating to define the compound angle;    -   a fusion cage wherein the first surface lies in a first plane        and the second surface lies in a second plane, the first and        second planes being non-parallel in cross-section along a        longitudinal axis and in cross-section along an axis generally        perpendicular to the longitudinal axis;    -   a fusion cage wherein the cage body comprises a longitudinal        plane along a longitudinal axis and a cross-sectional plane        along a cross-sectional axis that is generally non-parallel to        the longitudinal axis, the cage body being non-symmetrical about        either of the longitudinal plane or the cross-sectional plane;    -   a fusion cage wherein the cage body comprises a first surface        and a second surface coupling the plurality of surfaces, the        first surface defining a first surface area and the second        surface defining a second surface area, wherein the first and        second surface areas are different;    -   a fusion cage wherein the cage body defines a trapezoid or        trapezium in a cross-sectional plane that is generally        perpendicular to a longitudinal axis;    -   a fusion cage wherein the trapezoid or trapezium gets smaller        along the longitudinal axis from a first end to a second end;    -   a fusion cage wherein the cage body defines a second trapezoid        or trapezium in a second cross-sectional plane that is generally        perpendicular to a longitudinal axis, the cross-sectional plane        and the second cross-sectional plane being different in shape or        area;    -   a fusion cage wherein a first surface of a first vertebrae        cooperates with a second surface of a second vertebrae to define        the disk space, the cage body comprises a top defining a top        surface for engaging the first surface of the first vertebrae        and a bottom surface for engaging the second surface of the        second vertebrae, wherein the cage body is adapted to cause the        top and bottom surfaces of the cage body to engage the first and        second surfaces substantially flush after the fusion cage is        inserted into the disk space at an angled or diagonal        trajectory;    -   a fusion cage wherein the cage body comprises at least one        channel or slot generally parallel to a longitudinal axis of the        cage body, the at least one channel or slot being adapted for        receiving an insertion instrument;    -   a fusion cage wherein the cage body comprises at least one        aperture adapted for receiving an insertion instrument;    -   a fusion cage wherein the insertion instrument comprises indicia        to facilitate proper placement of the fusion cage;    -   a fusion cage wherein the plurality of surfaces comprise a first        surface that lies in a first plane and a generally opposed        second surface that lies in a second plane, the first and second        surfaces cooperating to define a compound angle;    -   a fusion cage wherein the compound angle is adapted to cause the        first and second surfaces to engage the first and second        vertebrae substantially flush when the fusion cage is inserted        at an angled or diagonal trajectory into a disk area;    -   a fusion cage wherein each of the plurality of surfaces        comprises an opening, the cage body having at least one of a        longitudinal slot or an opening adapted to receive a surgical        instrument;    -   a fusion cage wherein the cage body comprises a longitudinal        axis and a cross-sectional axis, each of the first and second        surfaces cooperating to define a first angle along the        longitudinal axis and a second angle along the cross-sectional        axis, each of the first and second angles being an acute angle;    -   a fusion cage wherein the first and second angles are different;    -   a fusion cage wherein the cage body is adapted such that when it        is inserted substantially diagonally or angled with respect to        an anterior-posterior axis, the first and second surfaces engage        the first and second vertebrae substantially flush;    -   a fusion cage wherein the first and second vertebrae cooperate        to define a second compound angle, the second compound angle        being adapted so that the first and second surfaces engage the        first and second vertebrae substantially flush when the cage        body is inserted into s disk area substantially diagonally or        angled with respect to an anterior-posterior axis;    -   a fusion cage wherein the first and second angles are different;    -   a fusion cage wherein the cage body comprises a shape that is        polygonal and non-circular in any plane;    -   a fusion cage wherein the plurality of surfaces comprises a        first planar surface and a generally opposed second planar        surface, the cage body is symmetrical about a diagonal axis        across the first planar surface;    -   a fusion cage wherein the fusion cage is symmetrical about a        longitudinal horizontal plane;    -   a fusion cage wherein the fusion cage is asymmetrical about a        longitudinal horizontal plane;    -   a fusion cage wherein the fusion cage is asymmetrical about a        longitudinal vertical plane;    -   a fusion cage wherein the fusion cage is asymmetrical about a        longitudinal vertical plane;    -   a fusion cage wherein the at least one aperture defines a        plurality of lateral slots;    -   a fusion cage wherein the plurality of lateral slots comprise        different dimensions to receive a plurality of projections,        respectively, of a surgical instrument, the plurality of        projections being adapted or sized to generally complement a        size of the plurality of lateral slots;    -   a method for fusing bones wherein the method further comprises        the step of providing a cage having the first and second        surfaces that cooperate to define a compound angle to provide a        biplanar angulation;    -   a method for fusing bones wherein the method further comprises        the step of providing a cage having a cage body comprising a        longitudinal plane along a longitudinal axis and a        cross-sectional plane along a cross-sectional axis that is        generally perpendicular to the longitudinal axis, the cage body        not being volumetrically symmetrical about either of the        longitudinal plane or the cross-sectional plane;    -   a method for fusing bones wherein the method further comprises        the step of providing a cage having a first surface and a second        surface and a first side and a second side coupling the first        and second surfaces, the first side defining a first side area,        the second side defining a second side area, wherein the first        and second side areas are different;    -   a method for fusing bones wherein the method further comprises        the step of providing a cage that defines a trapezoid or        trapezium in a cross-sectional plane that is generally        perpendicular to a longitudinal axis;    -   a method for fusing bones wherein the method further comprises        the step of providing a cage having a first surface generally        opposed to a second surface, the first and second surfaces        defining a compound angle and cooperating to define a biplanar        angulation;    -   a method for fusing bones wherein the method further comprises        the step of providing a cage with the first surface lying in a        first plane and the second surface lying in a second plane, the        first and second planes being non-parallel and defining a        plurality of acute angles;    -   a method for fusing bones wherein the inserting step occurs        during a posterolateral approach;    -   a method for fusing bones wherein the method further comprises        the step of providing a plurality of different sized cages from        which a user selects the cage;    -   a prosthetic implant system wherein the fusion cage has a        plurality of slots and the insertion tool comprises a plurality        of projections adapted for receiving in the plurality of slots;    -   a prosthetic implant system wherein the plurality of slots have        different dimensions and the plurality of projections generally        complement the shape of the plurality of slots;    -   a prosthetic implant system wherein the fusion cage comprises a        threaded aperture, the insertion tool comprising a threaded        member for screwing into the threaded aperture to secure the        fusion cage to the insertion tool;    -   a prosthetic implant system wherein the insertion tool comprises        indicia to facilitate proper placement of the fusion cage;    -   a prosthetic implant system wherein the fusion cage has a        plurality of slots and the insertion tool comprises a plurality        of projections adapted for receiving in the plurality of slots;    -   a prosthetic implant system wherein the plurality of slots have        different dimensions and the plurality of projections generally        compliment the shape of the plurality of slots;    -   a fusion cage wherein the plurality of surfaces cooperate to        define a biplanar angulation;    -   a fusion cage wherein the cage body has a first surface        generally opposed to a second surface, the first and second        surfaces cooperating to define a compound angle and defining a        biplanar angulation;    -   a fusion cage wherein the at least one of the first or second        surfaces are arcuate or convex in cross-section;    -   a fusion cage wherein a first surface and a second surface        converge along a longitudinal axis and in a direction generally        perpendicular to the longitudinal axis, the first and second        surfaces cooperating to define a compound angle; and    -   a fusion cage wherein a first surface lies in a first plane and        a second surface lies in a second plane, the first and second        planes being non-parallel in cross-section along a longitudinal        axis and in cross-section along an axis generally perpendicular        to the longitudinal axis.

While the method herein described, and the form of apparatus forcarrying this method into effect, constitute preferred embodiments ofthis invention, it is to be understood that the invention is not limitedto this precise method and form of apparatus, and that changes may bemade in either without departing from the scope of the invention, whichis defined in the appended claims.

1. A fusion cage comprising: a cage body having a plurality of surfaces;said plurality of surfaces cooperating to define a multi-planarangulation adapted to achieve substantially flush fitment in a diskspace between adjacent vertebrae when said fusion cage is inserted insaid disk space. 2-31. (canceled)
 32. A method for fusing bones, saidmethod comprising the steps of: providing a cage adapted to be insertedinto a disk area substantially diagonally or in an angled direction withrespect to an anterior-posterior axis, said cage having a first surfacelying in a first plane and a second surface lying in a second plane; andinserting said cage in said substantially diagonal or angled directionsuch that said first and second surfaces engage a surface of a firstvertebrae and a second vertebrae substantially flush.
 33. The method asrecited in 32 wherein said method further comprises the step of:providing a cage having said first and second surfaces that cooperate todefine a compound angle to provide a biplanar angulation.
 34. The methodas recited in 32 wherein said method further comprises the step of:providing a cage having a cage body comprising a longitudinal planealong a longitudinal axis and a cross-sectional plane along across-sectional axis that is generally perpendicular to saidlongitudinal axis, said cage body not being volumetrically symmetricalabout either of said longitudinal plane or said cross-sectional plane.35. The method as recited in claim 32 wherein said method furthercomprises the step of: providing a cage having a first surface and asecond surface and a first side and a second side coupling said firstand second surfaces; said first side defining a first side area, saidsecond side defining a second side area, wherein said first and secondside areas are different.
 36. The method as recited in claim 32 whereinsaid method further comprises the step of: providing a cage that definesa trapezoid or trapezium in a cross-sectional plane that is generallyperpendicular to a longitudinal axis.
 37. The method as recited in claim32 wherein said method further comprises the step of: providing a cagehaving a first surface generally opposed to a second surface, said firstand second surfaces defining a compound angle and cooperating to definea biplanar angulation.
 38. The method as recited in claim 37 whereinsaid method further comprises the step of: providing a cage with saidfirst surface lying in a first plane and said second surface lying in asecond plane, said first and second planes being non-parallel anddefining a plurality of acute angles.
 39. The method as recited in claim32 wherein said inserting step occurs during a posterolateral approach.40. The method as recited in claim 32 wherein said method furthercomprises the step of providing a plurality of different sized cagesfrom which a user selects said cage.
 41. A prosthetic implant systemcomprising: a fusion cage comprising a cage body having a plurality ofsurfaces, said plurality of surfaces cooperating to define amulti-planar angulation adapted to achieve substantially flush fitmentin a lordotic disk space between adjacent vertebrae when said fusioncage is inserted in said lordotic disk space; and an insertion tool forsecuring to said fusion cage to permit a user to insert and place saidfusion cage into a disk area using a posterolateral approach. 42-52.(canceled)